John Garfield was borrowed from Warner Bros. by RKO Radio for the tense espionage melodrama . Garfield is cast as Kit, an idealistic Spanish Civil War veteran who survives two torturous years in a fascist prison. Upon returning to New York, Kit is pounced upon by Nazi agents, who hope to learn the valuable secrets that Kit would not reveal to his captors during his ordeal. Among the methods of persuasion utilized by the Nazis is the beautiful Toni (Maureen O'Hara in a masterpiece of against-type casting). But Kit is made of stronger stuff than the spies are used to, and eventually he is able to beat them at their own game. Walter Slezak costars as the mellifluous-but-deadly Dr. Skaas. was based on the best-selling novel by Dorothy B. Hughes.